Attachment E - Stormwater Management Report · MCU24/0112

Table 6 – SPP Appendix 2: Part 3 Construction Phase – Stormwater Management Design Objectives
for Emergency Spillways on Temporary Sediment Basins

            Drainage Structure                   Anticipated Operation Design Life and Minimum
                                                              Design Storm Event


                                                  <3 Months         3-12 Months          >12 Months

 Emergency spillways        on     temporary     1 in 10 year        1 in 20 year        1 in 50 year
 sediment basins                                ARI/10% AEP          ARI/5% AEP          ARI/2% AEP

Best practice erosion and sediment controls must be installed to minimise the discharge of sediment
laden runoff during construction and to achieve the objectives outlined in Tables 4-6. This is discussed
in the following section.
4.3.2 E ro sio n and Se dim en t Co ntr ol

Management of stormwater runoff during construction is necessary to avoid pollution of downstream
waterways from sediment and gross pollutant loading. Impacts of inadequate erosion and sediment
control downstream from the site include:

    •   traffic safety problems;

    •   blocked drains;

    •   local flooding problems;

    •   aesthetic pollution of drainage paths; and

    •   damage to local ecosystems.

Best practice erosion and sediment controls must be installed to minimise the discharge of sediment
laden runoff during construction. Erosion and sediment control plans shall be developed during detailed
design phase and must be continually maintained and amended as required to minimise environmental
harm.

Erosion and sediment control plans are based on three sets of control measures:

    •   drainage control;

    •   erosion control; and

    •   sediment control.
These control measures must be maintained in an effective operational condition. Sediment disposal
from site is to occur to the satisfaction of Noosa Council. Defects in erosion and sediment control
devices, such as sediment fences, are to be inspected and documented. Upon Inspection, the
Contractor is to determine whether the device should be replaced or repaired. Documentation is to
include how the damage was caused and what measures can be implemented to reduce the possibility
of repeat occurrences. Any damage to either permanent or temporary water quality control structures
or devices is to be immediately rectified at the contractor’s expense.
The effectiveness of the erosion and sediment control devices can be monitored by visual audits. All
ESC measures are to be inspected:

    •   at least daily (when work is occurring on site) or weekly (when work is not occurring on site);
    •   within 24 hours of expected rain; and



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